Various prepaid and other methods of payment are available to customers of wireless telecommunication services. When a prepaid amount in a customer's account is exhausted, the customer may replenish the amount by buying a new prepaid card, or by calling a toll-free number to make a payment or by paying an invoice. It may be desirable to make such replenishment methods secure and fraud-resistant without compromising convenience for customers that reside in wide-ranging service areas.
U.S. Pat. No. 6,236,851 discloses a prepaid security cellular telecommunications system. U.S. Pat. No. 6,185,545 discloses an electronic payment system utilizing an intermediary account. U.S. Pat. No. 6,144,847 discloses a wireless telephone with credited airtime.